The invention relates to a soft x-ray spectrometric imaging system and, more particularly to such a system employing a charge coupled device (CCD) for measuring the energies of single photons incident upon the elements of the CCD array.
In the past, soft x-ray spectroscopy and soft x-ray imaging have been regarded as mutually incompatible endeavors. The detection systems used to reproduce soft x-ray images or to record soft x-ray spectra have been different from one another and have been unable to perform both tasks simultaneously. Soft x-ray images have been obtained by detector arrays, each picture element (pixel) of which is sensitive to either the total energy falling upon it, or the total number of photons incident upon it. Examples of such images detectors are photographic film and microchannel plate arrays.
Soft x-ray spectroscopy has involved the use of either wavelength dispersive crystal or grating spectrometers, or non-dispersive energy sensitive photon counters, e.g., gas proportional counters or solid state detectors. None of these spectrometers has been capable of distinguishing between spectra of adjacent sources. In order to obtain the spectra of N adjacent sources, N consecutive measurements, one of each source, had to be made. This was a time consuming process. Often, the character of the spectra changed in a time interval which is short compared to the time required to make the measurements.
Recently, a class of gas proportional counters capable of some position discrimination has become available. These systems are extremely limited, however, in their spatial and spectral resolution capabilities. Of critical importance is the fact that no more than one photon may be incident upon the entire proportional counter during the interval within which the photon is processed. Thus, either one must accept an extremely slow rate of acquisition of data or one must design a cumbersome system consisting of very many independent sub-units. This state of affairs is unsatisfactory for applications in which the spectra of thousands of adjacent fields must be obtained simultaneously in a short time.
Accordingly, it is a primary object of the invention to provide a spectrometric imaging system for simultaneously measuring the spectra of a plurality of adjacent radiation fields.
A further object of the invention is to measure the energies of individual photons emitted from the plurality of adjacent radiation fields.
Another object of the invention is to provide a means for measuring the energies of individual photons from adjacent radiation fields of a radiation source and imaging the source.
These and other objects of the invention will become apparent from a review of the detailed specification which follows and a consideration of the accompanying drawings.